#include<bits/stdc++.h>
using namespace std;
long long n,s,a[200];
int main(){
	cin>>n;
	for (int i=1;i<=n;i++)
		cin>>a[i];
    for (int i=1;i<=n;i++)
    	if (a[i]>a[i-1]) s+=6*(a[i]-a[i-1])+5;
    		else s+=4*(a[i-1]-a[i])+5;
    cout<<s;
}